1. Field of the Invention
The present invention relates to components for breathing circuits and in particular to conduits for use in the limbs of breathing circuits. The invention also relates to methods of manufacturing such conduits.
2. Summary of the Prior Art
In assisted breathing, particularly in medical applications, gases are supplied and returned through conduits. Such conduits are ideally light and flexible to achieve the highest possible level of comfort for the patient. In the prior art, thin walled conduits are known which include helical or annular reinforcing ribs which act to give the conduit better resistance to crushing and pinching, while still allowing the conduit to be light and flexible. A cross section of the wall of an example of such a conduit is shown in FIG. 1.
It is advantageous to manufacture this type of conduit as a continuous process. In the prior art this is achieved by the spiral winding of a thin polymer tape (ribbon or film) onto a former such that the edges of adjacent layers overlap a small amount. A bead of molten polymer is then applied over top the overlapping edges welding them together and simultaneously forming the helical reinforcing ribs. A disadvantage with this forming technique is the difficulty welding several adjacent layers. This problem is especially severe when multiple layer conduit walls are to be formed. While combining the application of a molten bead with another secondary thermal welding process or applying the polymer to the former as a still molten plastic does go some way to alleviating this difficulty, these solutions add complexity to the tube former and may be difficult to achieve with very thin walls.